One would have to be observing from overhead to notice that the four little bunches of people are all moving in the same direction, with the same purpose.

Until they pass through the invisible barrier that Andrew persists in referring to as a Somebody Else's Problem Field. They've all been told where it is; there's no perceptible change in stepping across it. Everything looks the same.

Except that there are no other pedestrians on this side of the street. And when they all start to coalesce into one large phalanx, nobody on the other side of the street gives them a second glance.